Quartus 2 13.0 - 'Unexpected error in JTAG server -- error code 12'

I am using an Altera USB Blaster Rev C in attempts to load a Max II EPM570 using Quartus II 13.0 in JTAG mode. I am getting "Unexpected error in JTAG server -- error code 12". I am wondering what this means for starters, and potential ways to resolve it. The error happens shortly after the "programming flash memory at byte address X" begins. Any assistance would be greatly appreciated.